The use of prokaryotic cells to biosynthesize biologically useful macromolecules is known in the art. For example, Escherischia coli (E. coli) is routinely used to synthesize a wide variety of biological macromolecules, such as enzymes used in research, and hormones, such as insulin, used in therapeutics.
Prokaryotic synthesizers may have inherent limitations, however. For example, these cells lack some of the organelles present in eukaryotic cells, such as the endoplasmic reticulum and Golgi apparatus, which are necessary to modify proteins prior to their actual use by the organism. Such modifications include glycosylating a protein with a complex oligosaccharide en banc in the endoplasmic reticulum and then modifying the oligosaccharide in the Golgi apparatus. As a result, the biologically useful macromolecule produced by these organisms must be chemically modified prior to their use in eukaryotic organisms, such as humans.
Efforts to overcome these limitations have been made by using lower forms of eukaryotic organisms, such as yeasts, as biosynthesizers. Since these organisms are eukaryotic, they possess the organelles necessary to modify biosynthesized macromolecules such as proteins. However, these efforts have met with only limited success. For example, the lower forms of eukaryotic organisms, including yeasts, do not make all the modifications necessary to permit the use of the desired macromolecule in the intended eukaryotic organism. Thus further chemical modifications still remain to be performed prior to their intended use.